obscuring phenomenon

obscuring phenomenon

[əb′skyu̇r·iŋ fə‚näm·ə‚nän]
(meteorology)
In United States weather observing practice, any atmospheric phenomenon (not including clouds) which restricts the vertical visibility or slant visibility, that is, which obscures a portion of the sky from the point of observation.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.